1. Field of the Invention
The present invention relates to a device and a method for detecting a rest position of a revolving body bearing a two-level code such as a bar code, and more particularly, to a detector for detecting a stopped position of a bar code disk in an apparatus such as a camera, a film scanner or the like using a film cartridge having a bar code disk on its spool.
2. Description of the Prior Art
In recent years, various new photographic systems suitable for automatic cameras have been proposed. Some of the new photographic systems use new types of film cartridges which are different from conventional film cartridges.
Some of the proposed film cartridges have a disk (rotation body) which rotates integrally with a film take-up spool and is provided with a bar code representing attributes of the film. The use condition of the film, i.e. whether the film is unexposed, fully exposed, partly exposed, or developed can be known from the stopped position of the bar code on the disk.
It is necessary to provide cameras, laboratory apparatuses and reproducing apparatuses such as film scanners which deal with film cartridges of the above-described type with a detector for accurately determining the position of the bar code. Since accuracy of the determination depends on the set location of the detector and the determination process, it is necessary to set the detector at a proper location and to use a complicated determination process so that the determination is made more accurately. A location and a process that enable accurate determination of the stopped position of the bar code are required especially for popular cameras where the detector cannot be located very precisely.